Overload protection

Lamp loads

When switching on lamp loads, high starting currents occur that are limited by the output circuit.

Inductive loads

When switching off inductive loads, high induction voltages result from interrupting the current too quickly. These are limited by an integrated free-wheeling. Since the current reduces only slowly, a delayed switch-off can occur in many control applications. For example, a valve remains open for many milliseconds. Switch-off times are realized that correspond, for instance, to the switch-on time of the coil.

Protection against high induction voltages To protect against voltage peaks such as can occur when switching inductive loads, we recommend to provide suitable protective circuits (e.g. with the free-wheeling diode, RC combination or varistor) directly at the actuator.

Thermal shutdown

In case of a long-term overload and/or short-circuit, the output is protected by the thermal shutdown of the channel.
The output circuit limits the current. It maintains this current until the channel is strongly self-heating.
If the upper limit temperature is exceeded, the channel is switched off.
After the channel has cooled down to the lower limit value of the temperature, the channel is switched on again.
The output signal is clocked until the output is switched off by the controller or the short circuit is eliminated. The clock frequency depends on the ambient temperature and the loads on the other channels.

Short circuit or prolonged overload on one channel leads to an increase in the device temperature. If several channels are overloaded, this leads to a rapid increase in the device temperature. The overloaded channels are switched off when the upper limit for the device temperature is exceeded. The channels are only switched on again if the temperature falls below the lower limit values for both the device and the channel. The non-overloaded channels continue operating properly.